Initial work on Dart bindings for Mojo.

mojo/public/dart/bindings/lib/src/interface.dart

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+part of bindings;
+
+abstract class Interface {
+  core.MojoMessagePipeEndpoint _endpoint;
+  core.MojoHandle _handle;
+  List _send_queue;
+
+  Future<Message> handleMessage(MessageReader reader);
+
+  Interface(this._endpoint) {
+    _send_queue = [];
+    _handle = new core.MojoHandle(_endpoint.handle);
+    _handle.listen((int mojo_handle_signal) {
+      if (core.MojoHandleSignals.isReadable(mojo_handle_signal)) {
+        // Query how many bytes are available.
+        List result = _endpoint.query();
+        if ((result[0] != core.MojoResult.OK) && 
+            (result[0] != core.MojoResult.RESOURCE_EXHAUSTED)) {
+          // If something else happens, it means the handle wasn't really ready
+          // for reading, which indicates a bug in MojoHandle or the
+          // event listener.
+          throw new Exception("bytes query failed: ${result[0]}");
+        }
+        int size = result[1];
+
+        // Read the data and view as a message.
+        ByteData bytes = new ByteData(size);
+        _endpoint.read(bytes);
+        var message = new Message(bytes, null);
+        var reader = new MessageReader(message);
+
+        // Prepare the response.
+        handleMessage(reader).then((response_message) {
+          // If there's a response, queue it up for sending.
+          if (response_message != null) {
+            _send_queue.add(response_message);
+            if ((_send_queue.length > 0) && !_handle.writeEnabled()) {
+              _handle.toggleWriteEvents();
+            }
+          }
+        });
+      }
+      if (core.MojoHandleSignals.isWritable(mojo_handle_signal)) {
+        if (_send_queue.length > 0) {
+          var response_message = _send_queue.removeAt(0);
+          _endpoint.write(response_message.buffer);
+          if (_endpoint.status != core.MojoResult.OK) {
+            throw new Exception("endpoint write failed");
+          }
+        }
+        if ((_send_queue.length == 0) && _handle.writeEnabled()) {
+          _handle.toggleWriteEvents();
+        }
+      }
+    }, onDone: () {
+      _handle.close();
+    });
+  }
+
+  void buildResponse(Completer c, Type t, int name, Object response) {
+    var builder = new MessageBuilder(name, align(getEncodedSize(t)));
+    builder.encodeStruct(t, response);
+    c.complete(builder.finish());
+  }
+}